Catalytic hydrocarbon conversion process



April 25, 1944.

E. w. THIELE 2,347,299 l CATALYTIC HYDROCARBON CONVERSION PROCESS Filed Jan. 3l, 1941 2 SheehS-Shee't l Z/'ME U/YSTPEAM/VMJA/wfs April 25, 1944 E. w. THIELE 2,347,299

CATALYTIC HYDROCARBON CONVERSION PROESS Filed Jan. 31, 1941 2 s-heetssheet 2 Patented Apr. 25, 1944 CATALYTIC HYDROCABBON CONVERSION PROCESS Ernest W. Thiele, Chicago, lll., assignor to Standard Oil Company, Chicago, lll., a corporation of Indiana Application'January 31, 1941, Serial No. 376,766

10 Claims. R(CI. 1198-50) This invention relates to a catalytic hydrocarbon conversion process and apparatus therefor. It pertains more particularly to a ilxed bed catalyst system for the production of high octane number motor fuels. The invention is particularly applicable to the isoforming ofthermally cracked naphtha but it may also be applied to catalytic cracking, hydrogenation, dehydrogenation, reforming, aromatization, alkylation, gas reversion, etc. f

In many catalytic processes employing solid catalysts there is a'gradual decrease in catalyst activity from the beginning to the end of each particular run. If low space velocities are employed throughout the run the charging stock may be severely over-treated during the initial period with a resulting formation of .excessive amounts of coke, gases and undesirable heavy fractions. If high space velocities are employed throughout the run initial over-treatment may be substantially avoided but the extent of conversion may be too low for practical purposes at the end of a reasonable on-stream period-in other words, the on-stream period would have to be too short from the standpoint of a practical regeneration cycle. A' uniform space velocity throughout the conversion part of the cycle results in gradually changing product distribution, an excessively large amount of gas being produced in the initial stage and an excessively small amount of conversion being eiiected in the iinal stage of the reaction. This change in product distribution during the course of the run increases the diiculty of product fractionation. A fractionating column designed for the maximum gas and gasoline production cannot be operated eiiiciently or at designed capacity toward the end of the conversion step. It is impractical to alter, to any appreciable extent, the rate at which charging stock is introduced t such a conversion system because lthe pumps,

heat exchangers, pipe still furnaces, etc. should be designed and operated under fairly constant conditions. An object of my invention is to avoid initial over-treatment and final under-treatment of charging stocks in, a fixed bed catalyst conversion system without altering pipe still conditions or charging rates.- A further object is to obtain a more desirable product distribution in a catalytic conversion process, i. e., to minimize the formation of gases and other undesirable byproducts. In other words, my object is to obtain less coke, less gas and less undesirable heavy polymers per barrel of gasoline produced than has been possible in any prior fixed bed conversion system operating for a similar period of time.

As applied to the lsoforming process. the object of my invention is to obtain a'product of higher octane number than could be obtained by any prior fixed bed process operated for a "similar period of time. The isoforming process lcomprises the catalytic conversion of thermally cracked naphtha over particular catalysts under such conditions as to obtain a yield of about 95 to 99% and an octane number improvement `of about to 15 points, e g., from about 65 or 'I0 to about 75 or 80.

When a catalyst rst goes on-stream in' an isoforming process there is apparentlyr an overtreating since the isoformate initially formed does not have as high an octane number as the isoformate which is obtained after the initial ori-stream period. The amount of time required for reaching optimum octane number improvement diiers with different space velocities. With high space velocities it may be reached' after the first few minutes on-stream, at a space velocity of about 12 v./v./hr. it may be reached at about 2 to 6 hours on-stream and at space velocity of 6 v./v./hr. it may be reached at about 6 to 24 hours ori-stream. After the optimum octane number improvement has been reached at any space velocity there is a tendency for octane number improvement to fall on with increasing periods of time on-stream. The relationship between octane number improvement and ori-stream time at various space velocities is roughly and qualitatively shown in Figure 2.

An object of my invention is to provide a method and means for operating an isoforming system at uniform charging rates and pipe still conditions and at a plurality of optimum space velocities whereby maximum octane numbersmay be produced throughout a relatively long period of time. Other objects of the invention will become apparent from the following descrip-y tion.

In practicing my invention I employ a plurality of groups of catalyst beds each group comprising a plurality of catalyst beds connected in parallel so that one group of bedsfmay be onstream while another group of beds is undergoing regeneration.- In the on-stream period I rst pass the charging stock vapors through one bed of the group. then I discontinue the now through the first bed and charge the vapors through anv other bed using in both yinstances a sumciently high space velocity to avoid appreciable overtreating. I then dividethe charging stock vapors' may use any number of beds in each group and' I may pass the charging stock vapors through each each bed or sub-group of beds separately at a relatively high space velocity and then pass the catalyst through more of said beds connected in parallel at relatively lower space velocities s o that initial over-treating is substantially eliminated, conversion rates are substantially maintained, losses to gas. coke, etc. are materially ,reduced, the load on the fractionating system is made more uniform and the quality of the resulting gasoline fractions is increased.

The invention will be more clearly understood from the following detailed description read in connection with the accompanying drawings which form a part of this speciiication and in which Figure 1 is a chart illustrating the principle of my invention as applied to catalytic cracking or other conversion processes;

Figure 2 is a chart illustrating the principle of my invention as applied to isoiorming; and

Figure 3 is a diagrammatic flow sheet illustrating a preferred apparatus for .practicing my invention.

When gas oil is catalytically cracked over silicaalumina type catalysts at temperatures of about 800 to 1000" F. the percent of conversion to gasoline is dependent upon the space velocities and the on-stream reaction time. Figure 1 is a cha'rt which roughly and qualitatively illustrates how conversion falls oil with reaction time on-stream at dierent space velocities. With percent of conversion plotted on a linear scale and time on-stream plotted on a condensed scale, which more nearly approaches a logarithmic scale, it has been found that the lines of constant space velocity are substantially parallel ,to each other and that there is an enormous increase in the initial over-treatment from space velocities of about 2 volumes of oil per volume ,of catalyst space per hour (hereinafter called v./v./hr.) to space velocities o! about 0.2 v./v./hr. Thus the conversion obtained at 1.8 v./v./hr. roughly falls along line mm ing in the initial period causes a decomposition of some of the cracked products sol that the actual percent conversion line is pluim' instead of mmm'. The cross-sectioned area mpio; indicates losses to gas, etc. due to over-treatment.

At a space velocity of 0.9 v./v./hr. the percent conversion will fall along the line nn' but since the converted products will be decomposed due to over-treating in the initial period, the actual gasoline production will fall along the line pzozn' except that the slight over-crackand the losses to gas, etc, will be represented by the shaded area M7202.

At a space velocity of 0.45 v./`v./hr. the percent conversion will fall along the line rr'Y but the actual gasoline production will be along the line maar', the losses to gas, etc. due to over-treating being represented by shaded area rpaoa. At 0.225 v./v./hr. the percent conversion will be along line ss',A the actual gasoline production will be along the line p4o4s' and the lossesdue to over-treating and decomposition in the initial treating period will be represented by shaded area smal. Objects oi my invention are to eliminate to the greatest practical extent the losses to` gas, etc. that are represented by the shaded areas hereinabove rel ierred to, to provide a system wherein theconversion to gasoline will be substantially constant and to accomplish these results without appreciably changing the amount or 'temperature of charging stock vapors in the pipe still Itransfer line. I accomplish these objects by providing a plurality of catalyst beds connected for individual or parallel flow in a unitary group. l Thus assuming that there are eight catalyst beds, A, B, C, D, E, F, G, H, each of one unit volume and that I am charging 1.8 unit volumes of gas oil per hour to the system, I may route the charging stock vapors through the catalyst beds as follows:

Sequence Catalyst bed onnegm v2 Diggy Mnutea All chambers... 100 0.225

represented by shaded area rpsy'z. The nal conversion step is along the line yaourt which maintains substantially the same gasoline-conversion and avoids the enormous losses represented by shaded area spiga. The total elapsed time will .be about six hours which provides ample time for regeneration which, of course, may be effected with all beds connected in parallel. If during this six hours the gas oil had been distributed in parallel over all eight catalyst beds, the overall space velocity would have been 0.225 and the loss to gas, etc. would'be that represented by shaded area spiga. My invention thus provides a method for eliminating this large loss due to over-treating and for maintaining substantially uniform gasoline conversion throughout the desired onstream reaction period.

It should be understood, of course, that Figure 1 is diagrammatic and illustrative and that I do not limit myself to any particular number of sequences, any particular space velocities in each sequence or any particular time for eilecting conversion in each sequence. 'I'hese variables will differ with various charging stocks, catalysts and conversion conditions and may be determined by preliminaryexperimens for each stock and each conversion system. For practical reasons it may be desirable to employ the beds two at a time in the first conversion steps, four at a time in the second, etc, or four at a time in theviirst convervsion steps and all eight in the second step, The

essential feature ofthe invention is the use of a plurality of catalyst beds which are first operated individually or in sub-groups and thereafter operated in parallel.

General operating conditions for, catalytic cracking rst in individual beds (or sub-groups) and then in parallel (or groups) are as followsz' By using l2 beds in each of two or more groups I may operate first with the .beds connected two cracked naphtha per hour in the following sequence:

Sequence Catalyst bed on'glream `v1gy Hours* V./v./hr.

2 24 2 24 2 24 2 24 4 12 E+F+G+H. 4 l2 All chambers 8 6 By operating the isoforming process in the above 1 2 l5 sequence of vsteps I not only avoid over-treating in the initial part of the conversion but I operate at the peak of the octane number curves at each time interval and thus obtain an overall higher octane number gasoline than would be at a time, then three at a time, then four at a 20 produced if the` entire system had been ontime. The sequence of steps and general operating conditions for such `a. catalytic cracking stream for the entire period of time at a space velocity of 6 v./v./hr. General operating condisystem might be as follows: tions for isofornung irst 1n individual beds (or I Sequence Catalyst bed Time on-stream Space velocity 5-15 min. e. g. 10 min. 1.8 v./v./hr. 5-15 min. e 1.8 v./v./hr. 5-15 min. e. 1.8 v./v,lhr. 5-15 mm e 1.8 v./v.lhr. 5-15 mm e 1.8 v./v./hr. 5-15 mln e g. 1.8 v./v. r. 10-20 mm e. g. 1.2 v. v./hr. llimm e. g. 1.2 v./v./hr. 10-20 min e. g. 1.2 v.[v./hr. 10-20 mm e. g.`1.2 v./v./hr. 15-30 mm e. g. .9 v./v./hr. 15-30 mln e. g. .9 v.,lv.lhr. I-l-J-I-K-l-L 15-30 min. e. g. .9 v./v./hr. A+B+C+D+E+F 15-30 min. .4r-l v./v./hr. e. g. .6 v./v./hr. G+H+I+J+K+L 15-30 min. .4-1 v./v./hr. e. g. .6 v./v./hr. All l2 beds 15-30 mm. .2-.8 v./v./hr. e. g. 0.3 v./v./hr.

In the isoforining of thermally cracked naphsub-groups) and then in parallel (or groups) are tha invention has additional advantages and is 40 as follows:

even more attractive from a commercial stand'- point because of the relatively long periods of onstream timesand the consequent ease of valve changes., Since the yields in isoforming range from about to 98% the losses to gas, etc. due 45 to over-treating will not be as marked as in the case of catalytic cracking but will, nevertheless, be of commercial sigiiiiicance.n In isoforming, however, the outsanding advantage of my invention is illustrated by Figure 2 wherein the oc- 50 Y tane number of the product is plotted against the time on-stream in hours. With a space velocity of 24 v./v./hr. the generalshape of the On-stream time Space velocity r'f s er 12 catalyst beds were employed instead of 8 a more gradual change in space velocities is possible thus with 6 beds the sequence of steps and operating conditions might be as follows:

Sequence Catalyst bed Time oustream Space velocity l-4 hrs. e. g. 2 8-40 v./v./hr. e. g. Zi v./v./hr. 1-4 hrs. e. g. 2 8-4D vq'vJhr. e. g. 24 v./v./hr. l-4 hrs. e. g. 2 8-40 v./v./hr. e. g. 24 v./v./hr. 2-l0.hrs. e.. g. 4 h 6-30 v./v./hr. e. g. 16 v./v./hr. 2-10 hrs. e. g. 4 h 6-30 v./v./hi e. g. 16 v-./v./hr. 4-20 hrs. e. g. 6 h 4-20 v./v./hr c. g.' l2 v./v./hr.

octane number curve is represented by sii. At

Although the invent-ion is applicable to a wide a space velocity of 12 v./v./hr. the octane num- 65 variety of processes it will be described as apject of my invention is to operate an isoforming 7u system in such a mann'er as to obtain the benefit of each and all of the octane number peaks. This may be accomplished by employing the eight unit volume bedsystem hereinabove referred to pliedto isoforming. The charging stock'to the isoforming *process is a naphtha produced by thermal cracking, preferably of gas oil or heavier hydrocarbons from any source whatsoever. The

at'relatively high temperatures and low pressures. `Generally speaking, the'thermal cracking may be attemperatures of 850 to l F.

and it is preferably within the range of about by charging forty-eight volumes of thermally 75950 to '1050o F; The pressure may range from thermal cracking should preferably be effected atmospheric to 1000 pounds or more but it is preferably lower than 300 pounds per square inch. The thermal cracking may be on a once-through or recycling basis and the products of the thermal cracking should be fractionated to give an isoforming charging stock with an end point not higher than about 400 to 450 F. The initial boiling point of the isoforming charging stock is of no particular consequence and the stockl may include or exclude normally gaseous hydrocarbons. Such charging stock will usually have an octane number of about 65 to 70 and this octane number is increased by the'isoforming to a value of about 75 or 80.

Referring to Figure 3. the thermally cracked naphtha is introduced through line I and forced by pump I I through coils I2 of pipe still I3 where-l in it is vaporized and heated to give a transfer line temperature of about 800 to 1100, preferably about `925 to 975 F. and a transfer line pressure of about atmospheric to about 50 pounds per square inch, preferably about 10 or 15 pounds per square inch. From transfer line I4 the heated vapors may be passed to any one of a group of catalyst beds but with valve I 5 closed and valve I6 open these hot vapors are passed through manifold I1 and one or more of the valved lines I8 to one or more of the catalyst beds, A; B H. These catalyst beds may be of any desired size and shape, may be in tubular conduits surrounded by heat exchange fluids or arranged in any other manner known to the art but I prefer to employ horizontal catalyst beds about 10 inches to 10 feet, preferably about'21/2 feet, in thickness. The incoming vapors are introduced at the top oi eachbed and withdrawn from the base thereof underneath the screen or catalyst bed support.

The amount of catalyst in each bed will vary is roughly about 500 pounds of catalyst per hundred barrels of stock charged per hour to the pipe still furnace. When all of the stock is charged to beds A and B (valves a, b, aa and bb being open and valves.c to h being closed) the space velocity will be about 24 v./v./hr. When it is charged in parallel through beds A, B, C and -D` (valves a to d and aa to dd being open and valves e to h being closed) the vspace velocity will be about 12 v./v./hr. lWhen it is charged to all of the beds connected in parallel (all valves a to h and aa to hh being open) the space velocity will be about 6 V./V./hr. I prefer to operate the beds two at a time for two hours, then four at at time for four hours, then eight at a time for eight hours to give a total twenty-four hour onstream period. Alternatively, I` may operate the first four beds in parallel for a two hour period at 24 v./v./hr., then with the next four beds in parallel for a two hour period at 24 v./v./hr. and

finally with all eightbeds connected in parallell for a two to four hour period at a space velocity of about 12 v./v./hr. thus obtaining an on-stream time of six to eight hours. Other operating sequences will be apparent to those skilled in the art troni the above description.

'Ihe products o conversion are withdrawn v through lines I9 and manifold 20 (valve 2l being open and valves 22 and l1 being closed) and thence discharged through line 23 to a conventional fractionation system which may comprise a fractionating column and one or more stabilizers each provided with conventional reheatin means, reflux means. etc. The gasoline fraction may thus be separated from lighter and heavier hydrocarbons in any conventional manner.

It is undesirable for catalyst beds to remain in 5 contact with charging stock vapors during idle periods and I, therefore, provide a suitable purge gas system. 'I'he purge gas such as steam or tail gases from the system may be introduced through line 24, `passed through heating coil 25 and dis- 10 charged to manifold 26 at a temperature which is about the same as or somewhat higher than the reaction temperature. When the charging stock ow is discontinued through beds A and B and transferred to beds C and D, I may open valves a1 and bi in lines 21 to permit purging gas from line 26 to' displace the charging stock vapors within beds A and B. Similarly. purging gas is introduced through other lines 21 and valves c1 to h1 when the charging stock flow through the corresponding catalyst beds is discontinued. This hot purging gas may also be employed for maintaining the desired temperature in the catalyst beds during idle periods. A relatively small amount of purging gas is required for this purpose and such gas may be separated from the products in the fractionation system. f

While beds A to H are oni-stream, beds A' to H' are undergoingregeneration preferably while connected in parallel. Flue gas, which may be recycled from the system or produced in a generator or both, is introduced through line 28 and Y regulated amounts of an oxygen-containing gas, such as air, is introduced through line 29 to form the regeneration gas which may be passed by line 30 to manifold I'I' (valve 3l being open and valves I5 and 33 being closed). The catalyst may be regenerated in the conventional manner and the regeneration gases may be removed from the system through line 3l, valve 35 being open and valve 22 being closed. The regeneration i s preferably effected under' a pressure of about 100 pounds per square inch and at such a rate that the maximum temperature willY not exceed the safe limits for the particular catalyst which, in the present instance, may be about 1050 to 1100 F. After beds A' to H have thus beenl regenerated and purged with flue gas they may go on-V stream in the manner hereinabove described for beds A to H. regenerated by closing valve 3| and introducing the flue gas and air mixture through line 32 to manifold I1, valves 3i and 'I6 being closed and valve 33 being open. In this part of the cycle the regeneration gases are withdrawn through line 36 while valve 21 is open and valve 2I is closed.

It should be understood that au ofthe valves y may be automatically opened and closed at the desired time intervals by electrical or pnemnatic 00 means well known to the art and that the system will thus function continuously to supply a fairly uniform stream to the fractionation Y system. Over-treating is prevented-full utilization is made of the catalyst over a relatively long period of time and a higher octane number motor fuel or isoformate is produced than could be produced by operating the entire system at any xed space velocity for a corresponding period of time.

The catalysts employed for isoforming are catalysts may be prepared from acid treated bentonite by making adough of such bentonite and water, forming pellets, thoroughly drying said pellets and heating them to a temperature of about 350 to 1000 F. Catalyst be AtthistimebedsAtoHwlbepreferably of the silica-alumina Such Vthe hot vaporized charging stock t prepared by depositing alumina or other metal oxides on or in silica gel. Examples of such.

said iirst-named bed of catalyst while charging stock iiow is discontinued therethrough.

3. In a hydrocarbonconversion system employing a plurality of groups of catalyst beds, each group comprising a plurality of catalyst beds connected in parallel, the method of operation which comprises regenerating one group of catalyst beds while the other group of catalyst `beds is on-stream, preheating a charging stock to vaporize it and heat it to conversion temperature passing charging stock vapors through one cf the on-stream beds at a high space velocity to obtain desired conversion without substantial over-treating, continuing the treating until said to any solid catalyst which has a tendency to become coated with a carbonaceous deposit duringthe on-stream part of the cycle and to exhibit a gradual diminishing activity of the type generally illustrated in Figure l. The catalyst may be in granular or pelleted form. Generally f speaking, the same type of catalysts may be employed for catalytic cracking as are employed for isoforming. A

When my apparatus is employed for catalytic cracking the chief dierence in operation will be a slightly lower temperature. i. e., about 800 to 1000 F., preferably about 900 F., a lower space velocity, preferably ranging from about 2 v./v./hr. for the initial highly active portion of the cycle to about .2 v./v./hr.`for the nnal step when all beds are connected in parallel. The on-stream time in the case of catalytic cracking may employ an ihitia step of about 5 to 15 minutes, a second step o 10 to 30 minutes, etc. as hereinabove described. Various modincations and equivalent operationswill be apparent to those skilled in the art from the above detailed description and my invention is not limited `to the specic examples hereinabove set forth except as deilned by the following.

claims.

I claim: l. In a xed bed catalytic hydrocarbon conversion system wherein a plurality of catalyst beds are connected for both individual and par-` allel iiow, the method of operation which comprises preheating a charging stock to vaporize it and heat it to conversion temp'e ature, passing oughY at least one of said beds ata suniciently high space velocity to avoid substantial over-treating and to obtain a. desired conversion rate, continuing the treating therein until the catalyst becomes partially deactivated and the desired conversion is no longer obtained' at said high space velocity then discontinuing the ow through said bed and introducing the hotV vaporized charging stock into at -least one other bed at such high space velocity as to substantially avoid overtreating and to obtain a desired conversion rate, continuing the treating therein until the catalyst becomes partially deactivated and the desired conversion is no longer obtained, and subsequently passing the hot vaporized charging stock in parallel through both beds at a lower space velocity for effectively utilizing the partially deactivated catalyst and maintaining lthe desired conversion without substantially altering the charging rate to the conversion system or the conditions in the preheating step.

2. The method of claim l which includes the further step of passing a hot purging gas through catalyst becomes partially deactivated and the desired conversion is no longer obtained, then transferring the charging stock vapor feed toanother on-stream bed, continuing the treating in said other on-stream bed at a high space velocity until the catalyst therein becomes partially deactivated and the desired conversion is no longer obtained, purging reaction vapors from said first bed while the other bed is onstream, then passing charging stock vapors in parallel through both beds so that the space velocity through the partially spent catalyst beds l may be reduced without materially altering the amount of charging stock vapors charged to the group of on-stream catalyst beds and withoutasubstantially altering conditions in the preheating step.

4. The method of obtaining a desired conversionfor a relatively long period of time and for avoiding initial over-treating in catalytic processes employing catalysts having a tendency to become coated with carbonaceous deposits` during on-stream reactions and which exhibit a gradual diminishing activity with on-stream time, which method comprises subdividing a conversion zone into a plurality of sub-zones, introducing charging stock vapors to said conversion zone at a substantiallyl constant rate and at a substantially constant temperature, first operating the sub-zones individually until the catalyst therei'n'becomes partially deactivated, and thereafter operating said sub-zones in parallel whereby the space velocity in the subzones is reduced by the parallel operation of sub-zones containing partially deactivated catalyst.

5. The method of obtaining a desired conversion for a relatively long period of time and for avoiding initial over-treating in catalytic processes employing catalysts having a tendency to become coated with carbonaceous deposits during on-stream reactions and which exhibit a gradual diminishing activity with on'stream time, which method comprises subdividing a conversion zone into a plurality of sub-zones, intro-v ducing charging stock vapors yto saidconversion zone at a substantially constant rate and at substantially constant temperature, passing all of the charging stock through one of said subzones in a first initial treating period until the catalyst becomes partially deactivated, then passing -all of the incoming charging stock through a. second sub-zone until the catalyst treating period 4being substantially lowerthan l the space velocities'in the initial treating periods. 6. The method lof claim 5 which includes the further step of passing a purging gas through the ilrst sub-zone when the flow of charging stock vapors is transferred therefrom to said second sub-zone.

9. The method of claim 5 wherein the cohversion vis catalytic cracking, the temperature of conversion is about 800 to'1000 F. and the on-stream times and space velocities in the '1. The method of claim 5 wherein the cons treating steps are substantially as follows: version is the isoforming of thermally cracked naphtha, wherein conversion temperature is about 800 to 1100 F., and wherein the reaction ori-stream s times and space velocities in the conversion steps im v i are substantially as follows: lo

Mmu V./u./Ar. msmlaa 3 32 02% ,my stummWmaz: 1H@ 03m I Houra V./v./Ar. x5 geitnltmg 1:3 m 10. The method of claim 5 wherein the consub-wneslnpar'a'u': ..1222` z-zo 4.20 version is catalytic cracking, the temperature of conversion is about 800 to 100* F. `and the on- 8. The-method of claim '5w wherein the con. stream times and space velocities in the treatversionis the isoforming of thermally cracked 20 ing Steps are Substantially as follows: naphtha, wherein conversion temperature is about 800 to 1100 F., and wherein the reaction- I times and space velocities in the conversion Onfggm 2% steps are substantially as follows: 

